Doppler Imaging of Close Binaries

Many of the interesting spotted stars are in close binaries, where one can find almost any rotational period due to the rotational synchronization with the orbital motion. Binaries are thus good laboratories to study the impact of particular astrophysical parameters that nature usually does not make easily observable. On rapidly-rotating stars, we may indirectly resolve the surface by a tomographic imaging technique and map the surface temperature distribution as a proxy of the (predominantly radial) magnetic field. Binaries are not as straightforward to map as single stars and I will show some examples where it was successful and some where it failed. Eclipses help to further constrain the solution from line-profile variations and may give some clues on the amount of unresolved features in the images. I present one case of a bright giant of 100 solar luminosities in a close binary with even a deformed surface geometry but otherwise solar-type behavior. One of the basic goals is to learn about the impact of inter-binary magnetic fields on the evolution of binaries and stars in general and to provide conclusive constraints for numerical MHD models.